[ticket/11342] Mark active topics read when marking forums read

Marking forums read while viewing a category will also mark the active
topics inside that category read. Therefore, the active topics should also
be marked read. With this patch the ajax callback "mark_forums_read" will
check if the active topics id ("active_topics") exists and also mark
topics read if it does. As the active topics will only be displayed in
categories, which can't have any other topics, this is a proper approach.

PHPBB3-11342
[ticket/10896] Adds email validation to email settings in ACP

Adds a new validation type to the ACP validate_config_vars function
and implements it on the board_contact and board_email settings.

PHPBB3-10896
[ticket/10896] Move EMAIL_INVALID_EMAIL to common, replace EMAIL_INVALID

PHPBB3-10896
[feature/migrations] Make the container available to extension installers

This allows extensions to load and install migrations easily as per their
needs.

PHPBB3-11318
[feature/migrations] Automatically install/revert migrations for extensions

Migrations from ext/ext_name/migrations/ are automatically installed
when enabling the extension and automatically reverted when the
extension is purged.

PHPBB3-11318
[feature/migrations] Rebuilding migrations data on develop

So this is easy to merge later.

PHPBB3-9737
[feature/migrations] Replace database_update.php with migrations updater

PHPBB3-9737
[feature/migrations] Revert schema for migration data

PHPBB3-9737
[feature/migrations] Remove hardcoded language, use lang instead.

PHPBB3-9737
[feature/migrations] Make depends_on static to call it without dependencies

Move installing migrations to migration/install.php and handle figuring
out what migrations have been installed based on phpBB version.

PHPBB3-11318
[feature/migrations] Fix migrations installer, schema for schema_data.sql

PHPBB3-11318
[feature/migrations] Order the migrations schema in schema_data.sql

PHPBB3-11318
[feature/migrations] Comments for the return in the custom functions

PHPBB3-11318
[feature/migrations] effectively installed check for migration data

PHPBB3-9737
[feature/migrations] Automatically populate migrations table on install

PHPBB3-9737
[feature/migrations] Reports table schema changes in recent develop

PHPBB3-9737
[feature/migrations] Subdirectories for migration data

Organization will set you free

PHPBB3-9737
[feature/migrations] Correct depends_on

PHPBB3-9737
[feature/migrations] Remove user_msnm migration

PHPBB3-9737
[feature/migrations] Fix path to extension migrations

PHPBB3-11318